It is well known from the state of the art that life of a hair follicle is characterized by continual and cyclical transition between a growth stage of the follicle (anagen) in which, amongst other things, the development of the hair is observed (by virtue of the activity of the keratinocytes), a subsequent regression stage (catagen) in which the programmed death (apoptosis) of a considerable portion of the cells of the follicle takes place, and a third, quiescence stage (telogen) at the end of which the hair follicle returns to the anagen stage with the formation of a new hair shaft.
The duration of the various stages of the life cycle of the hair follicle depends substantially on its position on the body. For example, whereas in the scalp region, anagen lasts from two to eight years, compared with a period of a few weeks for the catagen stage and a few months for the telogen stage, in the eyebrow region, the anagen stage lasts for only a few months. This time ratio also determines the percentage of hair follicles which are present, on average, in the various stages of the cycle, for each region of the body. The durations of the various stages of the cycle, as well as the transition between one stage and another are regulated by complex biological interactions, the mechanisms of which are not entirely clear, between the various parts of the hair follicle and between the follicle and the surrounding epithelial environment. It is, however, known that these stages are affected by many endogenous and exogenous factors which act, directly or indirectly, on the hair follicle to lengthen or shorten the duration of each stage.
Many attempts have been made to identify factors causing an early entry into the catagen phase or disorders of the hair follicle and to provide actives for fighting these symptoms, however, with little success so far. It is believed that an active promoting hair growth and in particular being truly successful against hair loss would double the existing market for men's hair care products world-wide.
In this context reference is made to WO 94/09750 A1 (Unilever) disclosing a composition comprising (a) ornithine, its salts, hydrosalts and precursors and (b) cosmetically acceptable carrier. As set out in the specification (page 9) typical examples for suitable derivatives of ornithine are ornithine hydrochloride, L-cystinylornithine, L-ornitylcitrulline and the like. According to the teaching of the application the compositions are used topically to the bald or balding scalp in order to promote hair growth. However, the technical teaching of the document relates to the urea cycle, including its intermediate molecules, such as ornithine. The application neither teaches nor suggests the use of alpha-ketoglutarate or the combination of both ornithine and alpha-ketoglutarate.
More particularly, the concrete problem underlying the present invention has been to increase the anagen period of the hair follicles and to delay the decline of the catagen phase to provide hair follicles more time to grow. At the same time growth of the hair follicles should be stimulated along with an increase of the number of cells in the proliferative stage. Finally, the new compositions should avoid any increase in cell apoptosis.